Usability: Build better software with naive testers

It's 1:00 AM in the morning. I have spent several hours trying to debug a major issue on the image synchronization service of our product. An issue so trivial I am clueless where to look-up into. Is it on the windows service deployed on web server, or on the windows forms CRM module, or on stored procedures and web server, or a file system issue. Is it because it is because Windows Vista. Is it because of improper settings and configuration? Configuration where? Why is it failing only on one computer? Its works on my machine!!!

After diagnostics and testing I have found the culprit. Its on the name of folder where the windows app retrieved the images. The application has 4 source folders for its images to be uploaded, "small, "medium", "large", "tuhmbnail". From those folders do you know where is the error?

Call to action:
Better error, debugging, and informational messages.
Better logging and event diagnostics.
Better checking and input validations.
Better settings and configuration management.
Better communication with testers and users. 

Answer: The "tuhmbnail" must be "thumbnail". One of my user/tester is really a very very good tester. He' the kind of user that easily gets frustrated with computers. He's the kind of person that will destroy a computer if it does not work the way he wants it to be.